// Copyright 2014 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef CONTENT_RENDERER_GPU_FRAME_SWAP_MESSAGE_QUEUE_H_
#define CONTENT_RENDERER_GPU_FRAME_SWAP_MESSAGE_QUEUE_H_

#include <map>
#include <memory>
#include <vector>

#include "base/auto_reset.h"
#include "base/macros.h"
#include "base/memory/ref_counted.h"
#include "base/memory/scoped_vector.h"
#include "base/synchronization/lock.h"
#include "cc/output/swap_promise.h"
#include "content/common/content_export.h"
#include "content/renderer/message_delivery_policy.h"

namespace IPC {
class Message;
};

namespace content {

class FrameSwapMessageSubQueue;

// Queue used to keep track of which IPC::Messages should be sent along with a
// particular compositor frame swap.
class CONTENT_EXPORT FrameSwapMessageQueue
    : public base::RefCountedThreadSafe<FrameSwapMessageQueue> {
public:
    class CONTENT_EXPORT SendMessageScope {
    public:
        virtual ~SendMessageScope() { }
    };

    FrameSwapMessageQueue();

    // Queues message to be returned on a matching DrainMessages call.
    //
    // |policy| determines how messages are matched with DrainMessages calls.
    // |source_frame_number| frame number to queue |msg| for.
    // |msg| - message to queue. The method takes ownership of |msg|.
    // |is_first| - output parameter. Set to true if this was the first message
    //              enqueued for the given source_frame_number.
    void QueueMessageForFrame(MessageDeliveryPolicy policy,
        int source_frame_number,
        std::unique_ptr<IPC::Message> msg,
        bool* is_first);

    // Returns true if there are no messages in the queue.
    bool Empty() const;

    // Should be called when a successful activation occurs. The messages for
    // that activation can be obtained by calling DrainMessages.
    //
    // |source_frame_number| frame number for which the activate occurred.
    void DidActivate(int source_frame_number);

    // Should be called when a successful swap occurs. The messages for that
    // swap can be obtained by calling DrainMessages.
    //
    // |source_frame_number| frame number for which the swap occurred.
    void DidSwap(int source_frame_number);

    // Should be called when we know a swap will not occur.
    //
    // |source_frame_number| frame number for which the swap will not occur.
    // |reason| reason for the which the swap will not occur.
    // |messages| depending on |reason| it may make sense to deliver certain
    //            messages asynchronously. This vector will contain those
    //            messages.
    void DidNotSwap(int source_frame_number,
        cc::SwapPromise::DidNotSwapReason reason,
        std::vector<std::unique_ptr<IPC::Message>>* messages);

    // A SendMessageScope object must be held by the caller when this method is
    // called.
    //
    // |messages| vector to store messages, it's not cleared, only appended to.
    //            The method will append messages queued for frame numbers lower
    //            or equal to |source_frame_number|
    void DrainMessages(std::vector<std::unique_ptr<IPC::Message>>* messages);

    // SendMessageScope is used to make sure that messages sent from different
    // threads (impl/main) are scheduled in the right order on the IO threads.
    //
    // Returns an object that must be kept in scope till an IPC message containing
    // |messages| is sent.
    std::unique_ptr<SendMessageScope> AcquireSendMessageScope();

    static void TransferMessages(
        std::vector<std::unique_ptr<IPC::Message>>* source,
        std::vector<IPC::Message>* dest);

private:
    friend class base::RefCountedThreadSafe<FrameSwapMessageQueue>;

    FrameSwapMessageSubQueue* GetSubQueue(MessageDeliveryPolicy policy);

    ~FrameSwapMessageQueue();

    mutable base::Lock lock_;
    std::unique_ptr<FrameSwapMessageSubQueue> visual_state_queue_;
    std::unique_ptr<FrameSwapMessageSubQueue> swap_queue_;
    std::vector<std::unique_ptr<IPC::Message>> next_drain_messages_;

    DISALLOW_COPY_AND_ASSIGN(FrameSwapMessageQueue);
};

} // namespace content

#endif // CONTENT_RENDERER_GPU_FRAME_SWAP_MESSAGE_QUEUE_H_
